Question

Find the value for the discriminant for the following equation: (2x +1)(x – 3) = 0

Answer 1

Hey Jacky :)
Do you understand how to multiply out the bracketed terms?

Answer 2

We need this in standard form before we can look at the discriminant:
\(\Large\rm ax^2+bx+c=0\)

Answer 3

Yes. I do. I would get 2x^2-5x-3

Answer 4

Mmm ok great!

Answer 5

I am confused on what I should do next.

Answer 6

Our quadratic formula allows us to solve for x,
\[\Large\rm x=\frac{-b\pm\sqrt{\color{orangered}{b^2-4ac}}}{2a}\]

The discriminant is the orange part, that's all we're concerned with here.

Answer 7

I got 7, is that correct?

Answer 8

\[\Large\rm \color{orangered}{b^2-4ac}\]Usually we want to know if this `greater than` `equal to` or `less than` zero,
to find out information about the polynomials roots.

Answer 9

\[\Large\rm \color{orangered}{b^2-4ac}=(-5)^2-4(2)(-3)\]

Answer 10

Hmm 7 doesn't look quite right :o

Answer 11

so would it be 49? I do not square root the b^2-4ac part?

Answer 12

Correct :) No square root needed.
They just want the `value` of the discriminant (stuff under the root).

Yay good job \c:/

Answer 13

Alright, thanks! I understand now. :)

Answer 14

cool